Nanosecond

A nanosecond (ns) is an SI unit of time equal to one billionth of a second (10−9 or 1/1,000,000,000 s). One nanosecond is to one second as one second is to 31.71 years.

The word nanosecond is formed by the prefixnano and the unitsecond. Its symbol is ns.

A nanosecond is equal to 1000 picoseconds or 1⁄1000microsecond. Because the next SI unit is 1000 times larger, times of 10−8 and 10−7 seconds are typically expressed as tens or hundreds of nanoseconds.

Another early reference commonly given[2] is to Admiral Grace Hopper, who used to give out pieces of wire about a foot long to illustrate the eventual problem of building very high speed computers.[3] If it takes light a nanosecond to go a foot (in a vacuum, slower in copper), then a computer built with parts connected by half this distance, 15 centimetres (5.9 in) of wire, would take at least a nanosecond to send data to a part and get a response. The solution, developed in Hopper's lifetime, was first the integrated circuit and later the multi-core processor.

Light travels exactly 29.9792458 centimeters in 1 nanosecond. This is equivalent to 11.8 inches, leading some to refer to a nanosecond as a light-foot.[4] A light-foot is actually ~1.0167033621639674471063578257196 nanoseconds.[5]